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GM: trans..Blazer..park to drive or reverse , harsh 1-2 shift and 2

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GM trans model 4l60e in 1993 K5 Blazer. Truck has 285K miles ; 80K on GM reman trans. Recent symptom is harsh shift from park to drive or reverse , harsh 1-2 shift and 2-3 shift. All gears work including TCC lockup , all downshifts normal. MIL is off. I found multiple trouble codes in the history that seem random and do not make sense with the symptoms. I have been testing and trying to solve this issue for several weeks. The line pressure is too high all the time : 100 to 150 at idle in park ; as high as 250 idle in drive. I replaced the pressure control solenoid and the wire harness in the pan. I tested the TPS normal . I replaced the VSS. Is it possible the PCM has failed? How can I test it?

Welcome to just answer.com. I'm here to help you and your 100% satisfaction is my goal. If the pressure control solenoid is good and the wiring all checks out good you most likely have a faulty PCM,Connect an ammeter to the PCS solenoid circuit. Use a scanner to command different levels of amperage flow. If the ammeter shows a difference between commanded and the actual amp flow through the pressure control solenoid

Sorry , this is my first time using the program. I'm am still not sure how it works . I don't intend to discount your help. You have confirmed my thoughts on the direction to go. I don't have access to a GM scan tool , only an OTC Genesis scan tool. It will not allow me to command signals to a component.

I tried to reply last week . I guess it did not go through. My trans problem is still with me. I replaced the pcm , the trans internal harness , the press.cont. solenoid , the tcc solenoid ,the temp / pressure switch pack ; verified the external harness is good. verified voltage from the pcm for trans temp ( 5vdc) and for the pressure switches ( 12vdc). I am not certain the connections at the trans case are complete. I plan to drop the pan again and verify the voltage at each component. I got my credit card statement and found 3 charges for $33 each. Is this the way you do business?

I can't do that test with the old OTC scanner I have. The new Genisis does not have a connector for OBD1 systems. I tested the circuits on my new harness in the pan and found the leads to the temp sensor were reversed. I made the correction in the harness outside the trans and retested with the same problem. I verified today the grounds to the pins at the PCM connector. I am following drawings and test info from "ALLDATA" but some of the info conflicts with what I have on my vehicle.